You could probably find a short travel fork designed for a hybrid bike and put that on your cross bike. However, I havn't seen this happen at any races that I've been to. It's more typical for non-pro riders to use a mountain bike instead of a cyclocross bike to compete in cyclocross races. The shocks do soak up a bit of pedaling effort, which is why they tend to be less desirable. Most modern MTB shocks can be locked out, and that's probably preferrable for the terrain of most cyclocross courses.
Your best bet to reduce the effect of bumpy terrain is to adjust the tire pressure according to the conditions. You may want to consider tubeless tire systems to prevent pinch flats at lower pressures. Smooth tracks will warrant high pressures, but rough courses may be more optimal riding at lower pressure.
Pro races set tire size limit to around 33mm, however most non-pro events have very loose restrictions on actual tire size. So consider running larger tires at lower pressure if you are concerned about the jarring effects of the ride without suspension.